1. Field of the Invention
The present invention concerns filters of the kind including, in a filter body adapted to be connected to two successive sections of a pipe of any kind, a filter unit in the general form of a wheel extending transversely in the filter body, rotatable about the axis of the body and including a filter element which extends globally across the cross-section of the filter body, with, on one side of the filter unit, for local contraflow circulation of a cleaning fluid through its filter element, a circulation unit which extends along a radius of the filter unit and to which a pipe is connected.
2. Description of the Prior Art
Filters of this type have the particular advantage of a small overall axial size which enables them to be inserted, like a simple collar, into the pipe to be equipped, even in a congested environment, their filter body being then formed of a cylindrical shell with the same diameter as the pipe.
They are used to intercept debris or other solid elements of the most diverse kinds.
One of them is described in particular in U.S. patent application Ser. No. 143,634 filed Jan. 13, 1988 and granted as U.S. Pat. No. 4,814,076.
In the above U.S. patent the filter is in a pressurized pipe which in practise is an inlet pipe of the installation concerned, the latter having to be protected from debris, detritus or other solid elements conveyed by the corresponding flow.
The cleaning fluid circulation unit is disposed on the upstream side of the filter element in this disclosure and is therefore a suction unit.
The pipe to which this circulation unit is connected is thus an outlet pipe for the cleaning fluid.
Accordingly, the cleaning fluid is taken directly from the flow in which the filter element is immersed, that is to say the flow which, conveyed by the pipe concerned, passes through this filter element.
In U.S. Pat. No. 5,589,898 issued Feb. 4, 1997. it is proposed to dispose a filter of the same type on the outlet pipe of the heat exchanger in which solid cleaning elements circulate to constitute an interceptor device adapted to retain the solid cleaning elements so that they can be recycled.
The above filter then includes two circulation units disposed on respective opposite sides of the filter unit, one on the downstream side of the latter in the direction of the outgoing flow and the other on its upstream side, and are in corresponding relationship to each other, each of them being connected to a pipe, one to an inlet pipe and the other to an outlet pipe for the corresponding cleaning fluid.
In the above U.S. patent application the two circulation units employed are both horns, i.e. frustoconical troughs the cross-section of which decreases from the periphery of the filter unit to its axis.
This disposition, which avoids the need for suction, is globally satisfactory, in particular with reference to the relatively small overall axial size to which it leads in U.S. Pat. No. 4,814,076.
However, a general object of the present invention is a disposition which advantageously further reduces this overall axial size.